Looking for Grau Ancestors in Thuringia

Looking for Grau Ancestors in Thuringia

My third great grandfather was Johann Andreas Grau. b. 1771, d. 1840. He lived in Crispendorf, Thuringia, Germany, but no birth records have been found. He married Eva Marie Grau (b. 1776, d. 1848) and they had five sons: Johann Christian Gottlieb Grau (b. 1796, d. 1867), Johann Christian Friedrich Grau (b. 1809), Friedrich Carl August Grau (d. 1885), Johann Gottfried Grau, and Johann Carl Friedrich Grau. I'm interested in the where Johann and the branch of Graus who moved to Crispendorf were and where they were from. Thanks for any help.